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Journal of Systematics and Evolution 46 (2): 142–154 (2008) doi: 10.3724/SP.J.1002.2008.07107 (formerly Acta Phytotaxonomica Sinica) http://www.plantsystematics.com

Phylogenetic inference of the genus () in Hengduan Mountains based on chromosome counts and nuclear ribosomal DNA ITS sequences Qi-Zhi WANG * Xing-Jin HE ** Song-Dong ZHOU* Yun-Ke WU Yan YU Yun-Li PANG (Laboratory of Systematic and Evolutionary Botany, College of Life Science, Sichuan University, Chengdu 610064, China)

Abstract Hengduan Mountains are the diversity center for the genus Bupleurum of Apiaceae in China. This paper reports chromosome numbers of six species and two varieties of Bupleurum, and for four species and two varieties their chromosome numbers are reported for the first time. The phylogeny of Bupleurum was investigated based on the ITS region of the nuclear ribosomal DNA (nrDNA) of 14 taxa from the Hengduan Mountains, 3 taxa from the North China (Hebei and Heilongjiang), and 16 taxa from Africa and the Mediterranean region. Varia- tions in chromosome numbers and the ITS sequences were used to infer phylogenetic relationships between Bupleurum species in Hengduan Mountains. The results showed that the Hengduan Mountains might represent one of the frequency and diversity centers for Bupleurum. The ancestors of Bupleurum species in the Hengduan Mountains may be related to the woody B. fruticosum in North Africa, or the species in the western Mediterranean region. It is postulated that the ancestral population migrated into Hengduan Mountains through the Middle East and the Caucasus. Furthermore, the neo-endemic B. mundtii in South Africa appeared to be a close relative of the species in the Hengduan Mountains. In the trend of basic chromosome number evolution, x = 8 should be regarded as the ancestral basic number, while x = 6, 7 as the derived ones. The Bupleurum species in the Hengduan Moun- tains have been undergoing changes in the basic chromosome numbers or the ploidy level. The ITS phylogenetic tree showed that the Chinese species were divided into two clades: one with the basic chromosome number x = 8, and the other with x = 6, 7. The results rejected the previous infrageneric classification of Bupleurum in China. We further suggested to raise B. marginatum var. stenophyllum to species rank based on the combined evidence from morphology, karyology, pollen morphology, and the ITS phylogenetic tree. Key words Bupleurum, chromosome, Hengduan Mountains, ITS, phylogeny, .

The genus Bupleurum L., with about 180–190 phylogeny and classification are incomplete. species spreading in the North Temperate Zone Traditionally, the woody Araliaceae is regarded (mainly in Eurasia, Mediterranean and North Africa), as the ancestor of the herbaceous Apiaceae (Calviňo et is one of the largest genera of the family Apiaceae al., 2006). Woody B. fruticosum L. in North Africa is (Liu et al., 2003; Neves & Watson, 2004). Species the possible ancestor of the species in genus Bupleu- within Bupleurum are easily recognized by the parallel rum (Gruas-Cavagnetto & Cerceau-Larrival, 1978). A venation of the simple leaves, conspicuous bracts and hypothesis on the origin of Apiaceae suggests that B. bracteoles on the inflorescences. Pollen morphology fruticosum might have migrated northward into Eura- exhibits little variation in this genus. The fruit is sia through the Middle East (Plunkett et al., 1996b). oblong to ovoid-oblong or ellipsoid, slightly laterally However, Neves and Watson (2004) suggested that compressed and the mericarp is subpentagonal (rarely the genus Bupleurum originated in the western Medi- rounded) in cross section. Bupleurum is a primitive terranean. Although B. fruticosum was nested within genus in Apioideae in recent molecular studies the western Mediterranean clade, it was not the most (Plunkett et al., 19